A general, six degree-of-freedom model of a projectile of finite geometry and inertia traveling in a flexible, rifled or smoothbore gun tube has been developed. The model accommodates projectile spin, mass eccentricity, projectile/bore interfacial friction, elastic/plastic deformation of the projectile rotating band, and balloting--including bourrelet impact and rebound with the bore. The model is unrestricted regarding gun tube motion, and provides the ability to assess the mutual effects of projectile/gun-tube interaction when solved simultaneously with the equations of a compatible gun dynamics simulation, such as DYNACODE-G. The basic formulation has been compared with other projectile in-bore motion formulations and descriptions appearing in recent literature, and is considered to be the most general developed to date. In addition, the model has been correlated with experimental in-bore radar doppler data obtained from firings of a specially designed 37mm weapon, and has demonstrated excellent theoretical/experimental agreement.